It is known in the art to have a mobile station or mobile communications device in radio telecommunication with a radio telecommunications system having a plurality of system operators or service providers. Each of the service providers operates one or more networks, each network including a plurality of base stations. Each base station has one or more control channels on which control information is exchanged and one or more voice channels on which voice messages may be passed back and forth between the base station and the mobile station.
Conventionally, one of the service providers has agreed to provide the user of the mobile communications device with radio telecommunications services in accordance with a specific fee schedule. This service provider may be referred to as the home service provider, the base stations operated by this service provider may be referred to as the home base stations, and the areas covered by the home base stations may be referred to collectively as the home service provider coverage area. When the mobile station is in radio telecommunication with the home base stations, the cost of the telecommunication services is calculated according to the agreed fee schedule.
It is also common for the user of the mobile station to move the mobile station to a point outside of the home service provider coverage area into the coverage area of another service provider. If the mobile station is used to communicate with a base station of the other service provider, however, the other service provider typically assesses charges in addition to the charges provided for in the above-mentioned fee schedule for the use of its network by mobile stations which do not have service agreements with it. These charges are commonly referred to as roaming charges.
Because the user of the mobile station may not be immediately aware of the amount of such roaming charges, many users would prefer to forego sending or receiving any radio telecommunications messages while in another service provider's coverage area. Many mobile stations provide the user with a visual indication on an output device associated with the mobile station representative of the fact that the mobile station has been moved outside the home service provider coverage area. However, this requires the user to pay particular attention to the visual display before initiating communication with the radio telecommunication system.
Moreover, at the boundaries of the home service provider coverage area, signals may be received by the mobile station from base stations of both the home service provider and other service providers. Given varying signal strengths along these border coverage areas, the strongest signal may continuously change between the home service provider and other service providers. This may make it even more difficult for the user of the mobile station to ensure that only home base stations are being used for the transmission and reception of radio telecommunications messages.